The present invention relates to oil well tools of the type used to pack off the annular space between the tool and surrounding well bore and, specifically, to an improved seal compressor for controlling fluid communication from the interior of the tool to the exterior of the tool and from the regions above and below the set packer.
Well bore packers are tools which are suspended in a well bore, usually from a pipe or tubing string running to the well surface. Such devices include an expandable seal element known as a "packer" which is expanded radially outwardly to contact the surrounding well bore or a surrounding well conduit to thereby pack off a portion of the well annulus. In many such devices, the packer element is carried on a packer body which has a longitudinal bore for receiving a packer mandrel. The mandrel is slidably received within the longitudinal bore of the packer body and is spaced-apart from the body to provide a fluid flow path between the exterior of the mandrel and the interior of the packer body. By appropriate manipulation, the mandrel can be moved into contact with the packer body to seal off the fluid flow path from within the tool to the exterior of the tool and from the regions above and below the set packer. The sealed fluid flow path within the tool might then be used, for instance, to conduct pressurized fluid to a part of the tool which further anchors the tool in the well bore, or other tool operations.
One difficulty with prior designs was that the mandrel and associated pipe string often weigh thousands of pounds. If the point of contact between the mandrel and packer body was also the seal point to close off the fluid flow path, the seal was subjected to extreme compressive loading, thereby reducing seal life and leading to early seal failure. Other prior designs featured seals which were acted upon by the pressure differential which exists between the pipe string fluid pressure and the annular fluid pressure both above and below the packer seal. Such pressure differentials at times caused seal failure.
There exists a need, therefore, for a seal mechanism which is isolated from the load carrying portions of the mandrel and packer body and which is effective to seal off the fluid flow path between the mandrel and packer body regardless of the amount or direction of the pressure differential which exists across the set packer.